Reading the manual is the first priority
How to monitor the voltage and current between type-C devices?
1. Make sure the PD trigger switch on the meter is turned off.
2. Connect the charger and the meter with a type-C cable, and then connect the meter and the mobile phone (or something else) with another type-C cable.
3. If the screen didn’t light up, flip the cable on any side of the meter.

Features:

Basic USB Meter Features

–Voltage and current monitoring with 0.0001V, 0.0001A resolution, 0.05% precision.

–Interfaces supported for both USB-A and USB Type-C devices.

–Voltage and current curve painting with sample rate up to 100 samples per second.(Note: Curve painting mode only, recording cannot be done at that rate)